The primary goal of this research program is the understanding of how the vertebrate central nervous system processes sensory information and organizes behavioral responses. This research, based on previous ethological and neurobiological studies, will be conducted with two species of weakly electric fish. By utilizing intracelluylar recording, physiologically characterized neurons can be filled with lucifer yellow or HRP and structure-function relationships in laminated structures can be addressed. Using stimulus regimes effective in driving the Jamming Avoidance Response (JAR), midbrain neurons of Eigenmannia have been identified which are sensitive to spatially static modulations of signal amplitude and differential phase. While these studies have provided some insight into the functional differentiation of particular laminae and the relationship between cell morphology and function, a more complete understanding requires that additional stimulus parameters be considered. It is particularly important to characterize single units in the torus semicircularis and optic tectum with regard to their sensitivity to spatio-temporally varying modulations in signal amplitude and differential phase (i.e., sensitivity to the motion of resistive and capacitive elements). Sternopygus, a species closely related to Eigenmannia, provides a natural test of whether "sign-sensitive" neurons of the torus and "sign-selective" tectal cells are, in addition to their role in the JAR, basic elements in the processing of object motion information. While Sternopygus has a laminated electrosensory midbrain which appears, at a gross morphological level, indistinguishable from that of Eigenmannia, this species does not have a JAR. The finding of sign-sensitive cells and sign-selective units in the midbrain of Sternopygus would lend support to this notion. The functional significance of lamination as a central processing scheme is a problem of general relevance to vertebrate sensory systems. The results of this research program therefore should provide needed insight into central processing mechanisms in sensory systems of higher vertebrates.